Electromagnet with shading coil



May 9, 1939. G. c. ARMSTRONG Er Al. 2,157,844

ELECTROMAGNET WITH SHADING'GOIL Filed Aug.' 28, 1956 2 Sheets-Sheet 1 r @gz O o G ||||||u|||||| Immun!!! A IIIIIIIIIIIIIIII!! unummlm! Il!!! u! u Illllllllllllll lllll llll May 93 1939- G. c. ARMSTRONG 1j- AL 2,157,844

lELECTROMAGNET WITH SHADING`COIL 111111111l SZ Patented May 9, 1939 UNITED STATES PATENT 'OFFICE 2,157,844 ELECTROMAGNET WITH SHADING CIL Application August 28, 1936, Serial No. 98,323

Claims.

Our invention relates to magnetically-actuated switches or contactorsand it has particular' relation `to improvements in the design and construction of contactor actuating magnets of the 5 alternating-current energized type.

Generally stated, the object of our invention is to facilitate the manufacture, improve the performance and lengthen the life of such magnets.

A more specific object is to provide a magnet which is tilt and shock proof, requires a minimum of space, has an efficient torque curve and high 'opening speed characteristic and is so constructed that switches having different current capacity ratings may be constructed largely oi.' common parts. I

Another object is to facilitate an adjustment of the pull characteristics of the magnet.

A further object is to make improved provision for varying the thickness of theycore-part lami- 20. nation stacks.

A still nfurther object is to provide improved supporting and spacing means for the magnet winding.

An additional object is to facilitate the manu- 25 facture and installationV and to prolong the life ol' shading coils for the pole pieces of the magnet.

Our invention, together with additional objects and advantages will best be understood from the when taken in conjunction with the accompanying drawings, in which Figure 1 is a view in front elevation of acontactor utilizing a magnet which incorporates the several improvements of our invention.

Fig. 2 is a view in side elevation of the complete device of Fig. 1.

Fig. 3 is a view in side elevation of one of the sets of' contacts of the contactor of Fig. 1.

Fig. 4 is a view in iront elevation of a portion of the magnet showing how the stacks of corepart laminations may be increased.

Fig. 5 is a View taken along section line V--V` following description of a speciilc embodiment Fig. 11 is a diagram of curves showing the relation between winding position and torque characteristics of the magnet of Fig.-10.

Figs. 12 andv 13 are enlarged views of our improved form of shading coil as installed on one l of the pole pieces of the magnet of Figs. 1 and 2.

Fig. 14 is a showing of a at metal .link from which the shading coil may be formed, and

Figs. l5 and 16 are views showing how the link of Fig.. 14 is bent and installed in the pole l0 piece slots.

'Ihe contactor magnet which We have represented in the drawings as incorporating the several features of our invention forms a part of a/ three-pole contactor of the shaft-driven vertical- 1I lift type. As best shown by Figs. 1 and 2, this device comprises an inverted U-shaped frame I6 which supportsI stationary contacts I0 by means of a panel member 24. The cooperating movable contacts I2 are carried by a shaft bar 26 which, through bearings pins 28, isrotatably supportedbetween the lower Vends of the frame legs.

One end of this shaft bar carries the armature or movable core portion 30 of the device-actuating magnet. 'I'he stationary core portion 32 of the magnet is attached to the side of one of the legs of frame I6 and has a downwardly extending center leg around which the magnetizing winding I 4 is positioned.

In the construction illustrated, frame I6 is adapted to position the device contacts and magnet in full operative relation and to support the complete contactor from a mounting panel or other supporting structure (not shown). `This unit or self-contained form of construction is more completely described by our copending application, Serial No. 98,322, led August'28, 1936.

The circuit to be controlled (not shown) is connected with the stationary contacts through lugs and with the moving contacts through flexible shunts 22. Associated with each set of contacts IIJ- I2 is an arc box 23 supported by a blowout coil 25. These boxes form a part of an improved arc quenching equipment, more completely shown and described by our cppending application, Serial No. 98,324, led August 28, 1936. In order to better show the construction and arrangement of the device contact parts, the view of Fig. l illustrates only one of the three boxes 23 in position.

The improved actuating magnet of our invention is of the E-core vertical-lift type. That is, the E shaped stationary cord portion 32 is mount-v ed with the legs projecting downwardly while the cooperating armature or movable core portion 55 is arranged to be attracted upwardly. As long as the magnet winding is deenergized, gravity holds the armature in the lowermost position i1- lustrated (full lines in Fig. 2) in which the movable contacts I2 are separated vfrom the stationary members I Il.

Energization of the winding I4 from any suitable circuit (also not shown), attracts the armature upwardly into the position shown by the dotted lines in Fig. 2. This rotates the shaft bar 26 into the contact-engaging position thereby completing the controlled circuit. Springs 33 form a part of the'connections between the bar 26 and the movable contacts I2. When in the above-referred-to engaging position, the bar is advanced somewhat beyond the point of initialv contact touching.

This further motion compresses the springs' vhorizontal jars produce no tendency toward a vms change in position on the part of movable contacts I2. Tilts of 45 or more are found not to alter the operation of the device.

The use of an E-type magnet mounted in the manner shown to provide a vertical lift of its armature also economizes space.- For the production of a given torque through a given angle, this form of magnet is decidedly superior. It has the further advantages of being compact and mechanically rugged.

The vertical lift arrangement also affords the maximum speed of contact opening. When the armature 30 is released the rotative force transmitted to shaft bar 26 by comipression springs 33 is supplemented by the weight of the moving structure parts including that of armature 30. 'Ihe resulting high speed of separation lowers the time of contact burning and thereby increases the contact life.

In order to elevate the rate at which the moving parts accelerate upon the release of armature 30, this armature is made as light in weight as possible. This is accomplished by reducing its mass to a. minimum Without sacricing pull strength. In accomplishing this, we use high quality steel laminations and reduce to a negligible length the outer legs 36 of the armature member. The central leg 38 is adapted to project some distance up into the magnetizing winding I4, in order to strengthen the pull of the magnet. In order tolimit the downard travel of the magnet armature, a stop member 40 is provided. It engages with an extension of the bracket 42 by means of which the armature is connected with the shaft bar 26. To prevent sticking due to residual magnetism, a separating insert 44 of non-magnetic material is provided. The bracket 42 may be detached from the bar 26 Without releasing a cooperating bearing bracket 46. To prevent rebound, the armature stop is positioned .at the center of percussion of the movable assembly.

Themagnet construction illustrated has pull characteristics which effectively coordinate with the torquevrequirements of the contactor. This relation is illustrated in Fig. 9, in which curve 48 depicts the pulling eiort of the armature throughy the entire range of its angle of travel theta. The torque requirements of the actuated contactor are depicted by the straight line. curve portions therebeneath.

When the contactor is in the open position illustrated in Figs. l, 2 and 3, gravity alone constitutes the opposition to upward movement of the parts carried by shaft bar 26. Horizontal line 50 indicates the magnitude of this opposition. When the angle of opening has been decreased to point 52, the contact members engage. Due to the compression of springs 33, the force of opposition to upward movement abruptly rises. The upper end of line 52 represents the point at which it is just overcome. Further decrease in the. angle of opening additionally compresses springs 33 and requires an applied force which progressively increases. along the line 54. 'I'he upper end of this line represents the fully closed position of the device.

Our improved magnet enables the pick-up voltage to be substantially equal to the seal-in voltage. The pick-up requirements are designated by line 56 in Fig. 9 and the seal-in requirements by line 54. The curve 48 represents a pull curve that is characteristic of the armature torque throughout its angle of travel in closing upon the application of normal operating voltage to the magnet winding I4. A decrease in voltage on the winding I4 which causes the curve 48 to drop below the pull-in line 50 at the right hand end of the curve provides insuiiicient energy to cause the contactor to start to close when the magnet is thus insufficiently energized. On

the other hand,the illustrated characteristics permit the use of an angle of contact spring compression which is suflicient to give a large allowance forl contact wear and to provide an amply high initial contact pressure. The large angle between the contact sealing position at the left of the curve and the contact engaging position represented by the substantially vertical portion 52 of the load curve also increases the opening velocity andin this manner decreases contact wear. y I

Our improved :design allows contactors of different ratings to use common magnet parts. The larger ratings, of course, require higher pull characteristics than do the smaller. We have observed that these characteristics vary as a function of the thickness of the stacks of core part laminations. 'I'he intermediate thickness shown in Fig. 1 yprovides an intermediate pull curve 48. To ,elevate this curve, it is merely necessary to increase the core stacks to some greater value-'such as is illustratedv in 4.y

In our improved arrangement, the stationary member 32 ymay be increased to thickness 32' merely by he use of longer holding bolts 60. Similarly, Ile armature 36 may be increasedpto thickness'3 by removing from the side of sup- -.porting bracket 42 'the spacer 62 and extending the liminations along the entire length cf the supporting rivet 64. Exactly the same parts, therefore, are used in both cases. Should it be desired to narrow the laminations below the thickness shown in Fig. 1, this may be done by the use of shorter bolts 60 and a wider spacer 62. Adjustment through a very wide range is, therefore, possible.

Our improved construction also contemplates another method of changing the pull characterthe lower portion of the winding structure.

istic of the magnet. This is accomplished by positioning the winding I4 at different points along the length of the central core leg which it surrounds. `The effect of such positional variation is depicted by Figs. 10 and 11.

When the winding is mounted in the uppermost position in which its lower end aligns with the we prefer to utilize the form of winding support illustrated in Figs. 6 to 8, inclusive. This comprises a pair of brackets 10 which are attached to opposite sides of the tubular central member 'I2 of the winding land the top projecting portions of which are secured to the structure of core piece 32.

Attachmentl of the brackets to the winding spool is preferably effected in the manner shown in Pigs. 6 to 8. A projection 'I4 punched from the bracket body is passed throughv a cooperating opening in the wall of winding tube 'i2 and then bent upwardly into the position shown by the full lines in Fig. '7. The lower end of the bracket may also be flanged outwardly into contact with This provides a very firm and rugged form of support.

The upper portions of/the brackets are then held ln the desired position with respect to the core piece 32 by a bolt 18 or other securing means. By altering the point of attachment 18 vertically, the position of the longitudinal center of the winding may be varied axially along the length of the surrounded core leg. This permits a variation in the character of the pull in curve 48 to adapt the contactor to Widely varying torque requirements. Among these requirements are changes in the amount of gravity load and pickup torque which accompany'variations in core thickness. The range of adjustment of winding position may be further extended by substituting a slot 18' (Fig. 8) for the attaching holeL in the top of bracket 1U.

In order to provide Ventilating spaces between the winding and the surrounded core leg, we utilize the expedients shown in Fig. 5. Spacing in one direction is maintained by making the outer laminations 80 Wider than those which make up the body of the core leg. The'heads 82 of the rivet which holds the laminations together are projected suiciently to space the coil interior from the core leg inthe other direction.

The described combination` of winding. supporting and spacing means is found especially suitable for the illustrated application in which the requirements of rigidity and durability are unusually high. It is both simple and inexpensive and may be used in situations where the surrounded core leg extends in a direction other than the verticallydownward one shown.

Our invention also contemplates improvements in the construction and method of installation of shading coils for the magnet' core. Each ofV the represented shading coils is in the form of a closed conductor 84 which loops a portion of each of the faces of the outer poles of the stationary core portion 32 of the contactor magnet. Its function is to tide the torque over during the zero periods in the main flux which the alternating-current energizing winding I4 circulates through the core structure. It does this by carrying induced currents which result in local fluxes out of time phase with the main flux.

The riature of our improved form of construction is best illustrated by Figs. 12 to 16; Y Preferably, the single turn link member 84 is punched from a fiat sheet of brass, copper or other suitable metal. Opposite sides are then bent through an angle of the substantial order shown in Fig. 15. One of the unbent rsides of the section is then inserted in one of the pole piece slots 86 and the other unbent side is then placed in position in the second pole piece slot 88. The angle of the bend in the link sides is then increased to the point shown in Fig. 16. 'I'his may be done by striking with a suitable tool. of the thus distorted metal member serves to hold it firmly in place in the pole piece slots.

This form of construction results in an inexpensive shading coil having practically unlimited life. Increases in the cross sectional area of the polel piece, due to the hammering action of the armature, cannot introduce harmful stresses in the metal link. Increases in a direction parallel to the slot-inserted sides may readily be taken care of by making the length of these sides substantially great'er than required by the original installation. Increases perpendicular to the parallel slots are compensated for by the resiliency of the folds in the side members of the link. 'I'he resiliency also prevents vibration,

which is another frequent cause of breakage.

'I'his feature is of great importance particularly in applications such as illustrated where the pole pieces are subjected to frequent and severe pounding by the cooperating armature.-

Shading coils o-f prior art design are incapable of withstanding the resulting pole face spread.

ing without fracture. Our improved construction can remain in service practically indefinitely in such an application. It is also economical to manufacture and install.

The broad principles of our improved form of construction are applicable to shading coils formed from round or other conductors shaped differently from the rectangular sectioned variety illustrated. The relative positioning of the pole piece slots and the installation of the metal link therein in folded position are fundamental features which prolong the life and otherwise in' or bends formed in its side portions tending to change the angle of bend, the dimensions of and mounting for the link being such that the cross sectional area of the pole piece may be increased without imposing harmful stresses on the link.

2. In combination, an electromagnet having a pole piece provided with two slots in angularly different face portions, a shading coil comprising a metal link member having substantial bends in the central part of two opposite side portions so that the opposite ends thereof extend in dii'- The self resiliency ferent directions, the remaining opposite sides of said link being disposed in said slots and there held by the resiliency of said bends, the dimensions of said link member being such that the cross sectional area ofl the pole piece may be increased without imposing harmful stress on the link.

3. In combination, an electromagnet which has a slot in its face and a second slot in one of its sides, a shading coil comprising a. single-turn section, punched from a at sheet of metal, the central portions of two opposite sides of which are so bent that the opposite ends thereof extend in planes at a substantial angle to each other and the remaining sides of which are tted into said slots where they are so held by action of said bends that the cross sectional area of the pole piece may be increased without imposing harmful stress on the link.

4. In the application of a shading coil to the pole piece of an electromagnet provided with two spaced slots to receive it, the method which con sists in forming metal into a single-tum section, bending opposite sides of that section through a substantial angle, engaging one of thevunbent sides of the section in one of the pole piece slots, engaging the other unbent side in the'other polepiece slot, and increasing the angle of bend whereby to hold the section in place in the slots. 5. In the application of a shading coil to the pole piece of an electromagnet which has a slot in its face and a second slot in one of its sides, the method which consists in punching a singleturn section from a flat sheet of metal, bending opposite sides of that section through a substantial angle, engaging one of the unbent sides of the section in one of the pole-piece slots, engaging the other unbent side in the other polepiece slot, andso increasing the angle of bend as rmly to hol'd the section in place in the slots.

GEORGE C. ARMSTRONG. DELBERT ELLIS. 

